Field of the Invention
The present disclosure relates generally to tube-in-a-tube (Tube^2) electronic materials and electronic chemical sensors comprising Tube^2.
Background
One of the challenges and opportunities in nanoscience lies in developing the ability to utilize the electrical properties of nanomaterials in complex chemical systems such as solar cells, fuel cells, microprocessors, and sensors. In the context of sensing applications, there is hope that nanomaterials will allow for fabrication of electrical sensors capable of detecting ultralow concentrations of analytes, e.g., explosives (such as TNT, nitroglycerin, cyclotetramethylene-tetranitramine) and biomolecules (such as HIV), with ultrahigh selectivity such that trace interferents will not trigger false positives. Various nanostructures and strategies have been explored for meeting this challenge. Some of the most sensitive sensors are based on graphene and pristine single-walled carbon nanotubes (SWCNTs) (Kong et al., Science 2000, 287, 622; Chen et al., Proc. Nat. Acad. Sci. U.S.A. 2003, 100, 4984; Star et al., Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 921; Sorgenfrei, et al., Nat. Nanotechnol. 2011, 6, 126; Kim, et al., Adv. Mater. 2009, 21, 91; Li et al., J. Am. Chem. Soc. 2005, 127, 12484; Ganzhorn et al., ACS Nano 2011, 5, 1670; Cao et al., Adv. Mater. 2009, 21, 29; Kim, et al., ACS Nano 2011, 5, 2824; Forzani, et al., Small 2006, 2, 1283; Roberts et al., ACS Nano 2009, 3, 3287; Myung et al., Adv. Mater. 2011, 23, 2221; and Myung, et al., Adv. Mater. 2012, 24, 6081).
Some success has also been achieved with non-covalent functionalization of the surface with receptor molecules to overcome non-specific binding. (Chen et al., Proc. Nat. Acad. Sci. U.S.A. 2003, 100, 4984; Martinez et al., Nano Lett. 2009, 9, 530; and Pacios et al., Nanoscale 2012, 4, 5917). However, low long-term stability and incomplete surface coverage of non-covalent coatings remain general concerns for more demanding applications such as in vivo studies and those involving more aggressive chemical reactions that require a more stable and robust platform (Wang, et al., Am. Chem. Soc. 2011, 133, 11181). Covalent attachment of receptor molecules to the surface is an effective strategy for improving chemical selectivity. But the number of functional groups that can be covalently attached to a SWCNT sidewall or graphene surface is limited since covalent modifications quickly destroy their electrical properties (Goldsmith et al., Science 2007, 315, 77).
A double-walled carbon nanotube (DWCNT) consists of two concentric SWCNTs that exhibit complicated but relatively independent electronic properties (Shen et al., Nanoscale 2011, 3, 503). Field-effect transistors integrating individual, pristine DWCNTs have been shown to have high on/off ratios (>103) and exceptional conductivity (Liu et al., J. Am. Chem. Soc. 2009, 131, 62 and Bouilly et al., ACS Nano 2011, 5, 4927). Advances in synthesis (Endo et al., Nature 2005, 433, 476 and Qi et al., Nano Lett. 2007, 7, 2417) and purification of DWCNTs (Green et al., Nat. Nanotechnol. 2009, 4, 64 and Green et al., ACS Nano 2011, 5, 1459) have made it possible to fabricate high quality thin film devices. Particularly, recent experiments have shown that the electrical properties of inner tubes can be retained even after heavy functionalization of the outer wall by covalent chemistries (Bouilly et al., ACS Nano 2011, 5, 4927; Brozena, et al., J. Am. Chem. Soc. 2010, 132, 3932; and Piao et al., J. Phys. Chem. Lett. 2011, 2, 1577).
There exists a need for thin-film transistor chemical sensors having ultrahigh selectivity and sensitivity for the electrical detection of biomolecules and other chemicals.